Electrochemical Machining

• A popular application of electrolysis is the electroplating process in which metal coatings are deposited upon the surface of a catholically polarized metal. • ECM is similar to electro polishing in that it also is an anodic dissolution process. But the rates of metal removal offered by the polishing process are considerably less than those needed in metal machining practice . • Metal removal is achieved by electrochemical dissolution of an anodically polarized workpiece which is one part of an electrolytic cell in ECM. • when an electric current is passed between two conductors dipped into a liquid solution named as Electrolysis . • Electrolytes are different from metallic conductors of electricity in that the current is carried not by electrons but by atoms, or group of atoms, which have either lost or gained electrons, thus acquiring either positive or negative charges. Such atoms are called ions. Electrolytic dissolution of iron.

that is. voltage. is applied across them. • The movement of the ions is accompanied by the flow of electrons. • Both reactions are a consequence of the applied potential difference. toward the cathode.• Ions which carry positive charges move through the electrolyte in the direction of the positive current. that is. and are called cat anions. respectively. • The negatively charged ions travel toward the anode and are called anions. • A suitable electrolyte. in the opposite sense to the positive current in the electrolyte. through the gap between the electrodes to remove the products of machining and to diminish unwanted effects. from the electric source. of an electrolytic cell. usually at about 10 V. and a constant potential difference. such as those that arise with cathodic gas generation and electrical heating. aqueous sodium chloride (table salt) solution. is chosen so that the cathode shape remains unchanged during electrolysis.
. Working Principle
• the workpiece and tool are the anode and cathode. for example.
• The electrolyte is also pumped at a rate 3 to 30 meter/second.

for example. • the gap width along the electrode length will gradually tend to a steadystate value.02 millimeter/second toward the anode.• The rate at which metal is then removed from the anode is approximately in inverse proportion to the distance between the electrodes • As machining proceeds. • The current density must be high. a shape. roughly complementary to that of the cathode. Under these conditions. will be reproduced on the anode.
Schematic diagram
ECM Components (Power) • The power needed to operate the ECM is obviously electrical.
. and with the simultaneous movement of the cathode at a typical rate. There are many specifications to this power. 0.

– The current is dependant on the above parameters and the feed rate. • The electrolyte is stored in a tank. • The inlet pressure must be between 0. thus the voltage must be low to avoid a short circuit. ECM Components (electrolyte circulation system) • The electrolyte must be injected in the gap at high speed (between 1500 to 3000 m/min). • Relatively fast • Can machine harder metals than the tool
. • The control system uses some of this electrical power. • System also includes a filter.• The gap between the tool and the work piece must be low for higher accuracy. and treatment units. • The electrolyte system must include a fairly strong pump. ECM Components (control system)
• Control parameters include: – Voltage – Inlet and outlet pressure of electrolyte – Temperature of electrolyte. • There is no heat affected zone. • Very accurate. Advantages • There is no cutting forces therefore clamping is not required except for controlled motion of the work piece.15-3 MPa. sludge removal system.

Disadvantages • More expensive than conventional machining. • No heat affected zone. it can be used repeatedly with a high degree of accuracy. • Material has to be electrically conductive. • Sinking operations (RAM ECM) are also used as an alternative to RAM EDM. Products • The two most common products of ECM are turbine/compressor blades and rifle barrels. • Electrolytes may destroy the equipment.• Faster than EDM • No tool wear at all. • It is also used to make cavities and holes in various products. • It is commonly used on thin walled. Applications • The most common application of ECM is high accuracy duplication. • Better finish and accuracy. • Need more area for installation. easily deformable and brittle material because they would probably develop cracks with conventional machining.
. • Not environmentally friendly (sludge and other waste) • High energy consumption. Because there is no tool wear.

• Some of these mechanical characteristics achieved by ECM are: – Stress free grooves. cylinder cavities in engines).• Each of those parts require machining of extremely hard metals with certain mechanical specifications that would be really difficult to perform on conventional machines. – Any conductive metal can be machined. • Large cavities are more economical on ECM and can be processed in 1/10 the time of EDM. – High surface finish. Economics • The process is economical when a large number of complex identical products need to be made (at least 50 units). • Several tools could be connected to a cassette to make many cavities simultaneously.0005”. – Fast cycle time.
. – Repeatable accuracy of 0.e. – Any groove geometry. (i.